package com.leo.util;

import java.security.MessageDigest;
import java.util.Date;
import java.util.Random;

public class AccessTokenUtil {
	public final static String MD5(String s) {
		char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
				'A', 'B', 'C', 'D', 'E', 'F' };
		try {
			byte[] btInput = s.getBytes();
			// 获得MD5摘要算法的 MessageDigest 对象
			MessageDigest mdInst = MessageDigest.getInstance("MD5");
			// 使用指定的字节更新摘要
			mdInst.update(btInput);
			// 获得密文
			byte[] md = mdInst.digest();
			// 把密文转换成十六进制的字符串形式
			int j = md.length;
			char str[] = new char[j * 2];
			int k = 0;
			for (int i = 0; i < j; i++) {
				byte byte0 = md[i];
				str[k++] = hexDigits[byte0 >>> 4 & 0xf];
				str[k++] = hexDigits[byte0 & 0xf];
			}
			return new String(str);
		} catch (Exception e) {
			//e.printStackTrace();
			return null;
		}
	}

	public static String getRandomString(int length) { // length表示生成字符串的长度
		String base = "abcdefghijklmnopqrstuvwxyz0123456789";
		Random random = new Random();
		StringBuffer sb = new StringBuffer();
		for (int i = 0; i < length; i++) {
			int number = random.nextInt(base.length());
			sb.append(base.charAt(number));
		}
		return sb.toString();
	}

	public static String getAccessToken(String appid, String secretKey) {
		long date = new Date().getTime();
		String str = appid + secretKey + date + getRandomString(5),
				accessToken = AccessTokenUtil.MD5(str);
		//System.out.println("<getAccessToken>:");
		//System.out.printf("[%s]->[%s]\n", str, accessToken);
		return accessToken;
	}
	public static void main(String[] args) {
		System.out.println(getAccessToken("appid", "key") );
	}
}